Purification of a 41 kDa cod-allergenic protein

Influence of Proteins on the Absorption of Lipophilic Vitamins, Carotenoids and Curcumin - A Review

While proteins have been widely used to encapsulate, protect, and regulate the release of bioactive food compounds, little is known about the influence of co-consumed proteins on the absorption of lipophilic constituents following digestion, such as vitamins (A, D, E, K), carotenoids, and curcumin. Their bioavailability is often low and very variable, depending on the food matrix and host factors. Some proteins can act as emulsifiers during digestion. Their liberated peptides have amphiphilic properties that can facilitate the absorption of microconstituents, by improving their transition from lipid droplets into mixed micelles. Contrarily, the less well digested proteins could negatively impinge on enzymatic accessibility to the lipid droplets, slowing down their processing into mixed micelles and entrapping apolar food compounds. Interactions with mixed micelles and proteins are also plausible, as shown earlier for drugs. This review focuses on the ability of proteins to act as effective emulsifiers of lipophilic vitamins, carotenoids, and curcumin during digestion. The functional properties of proteins, their chemical interactions with enzymes and food constituents during gastro-intestinal digestion, potentials and limitations for their use as emulsifiers are emphasized and data from human, animal, and in vitro trials are summarized.

Isolation, characterization, and identification of proteins interfering with enzyme-linked immunosorbent assay of antibiotics in fish matrix

The interaction between some proteins and immune globulin has been confirmed as an important source of matrix interference with the immunoassay of fishery products, but detailed biochemical properties of these proteins have not been indicated. Two interference-inducing proteins (42 and 36 kD) in flounder were isolated, characterized, and identified. Their influences on the immunoassay of norfloxacin were confirmed by western blotting and enzyme-linked immunosorbent assay. The pI value and pH stability of the two proteins were also investigated. Using LC-MS/MS, the two proteins were identified as fructose-bisphosphate aldolase, and such results were partly verified by the aldolase activity of the 42 and 36 kD isolates. Considering the prevalence of these proteins (as multi-functional aldolase of muscles) in foods, these results would help to further understand the matrix effects in various immunoassays as well as the development of effective techniques to improve the efficiency of immunoassays.

Electrophoretic Behavior in Relation to the Structural Integrity of Codfish Parvalbumin upon Heat Treatment

This work evaluates the impact of heat processing of parvalbumin, a major fish allergen, on the consequences for quantitative analysis of this protein embedded in different matrices during heating (either isolated, in an aqueous extract, or in whole fillets) to assess potential health risks. It is shown that oligomerization of parvalbumin does occur, but only upon heat treatment above 80 °C. This coincides with the ability of the isolated protein to refold up to this temperature in a fully reversible way, as demonstrated by circular dichroism analysis. In autoclaved samples a disintegration of the protein structure is observed. The situation becomes different when parvalbumin is embedded in a matrix with other constituents, as in fish extracts or whole fillets. The electrophoretic analysis of parvalbumin (SDS-PAGE and immunoblotting) is largely determined by complexation with other proteins resulting in insoluble materials caused by the partial unfolding of the parvalbumin at elevated temperatures. This effect is more strongly observed for cod fish extract, compared to whole cod fillets, as in the latter situation the integrity of the tissue hampers this interprotein complexation. Moreover, it is shown by ELISA analysis of heat-treated samples that using blotting procedures where disintegration of complexes may be promoted, restoring some of the IgG-binding propensity, may provide false outcomes. It was concluded that antibody binding to parvalbumin is dominated by the potential to form heat-induced complexes with other proteins. The possibly less-soluble or extractable character of these complexes may provide confusing information regarding potential health risks of fish and fish protein-containing food composites when such heat-treated samples are analyzed by immunochemical assays.

Specific IgE to fish extracts does not predict allergy to specific species within an adult fish allergic population

BACKGROUND

Fish is an important cause of food allergy. Studies on fish allergy are scarce and in most cases limited to serological evaluation. Our objective was to study patterns of self-reported allergy and tolerance to different commonly consumed fish species and its correlation to IgE sensitization to the same species.

METHODS

Thirty-eight adult fish allergic patients completed a questionnaire regarding atopy, age of onset and symptoms to 13 commonly consumed fish species in the Netherlands (pangasius, cod, herring, eel, hake, pollock, mackerel, tilapia, salmon, sardine, tuna, plaice and swordfish). Specific IgE to these fish extracts were analyzed by ImmunoCAP.

RESULTS

Median age of onset of fish allergy was 8.5 years. Severe reactions were reported by the majority of patients (n = 20 (53%) respiratory and of these 20 patients, 6 also had cardiovascular symptoms). After diagnosis, 66% of the patients had eliminated all fish from their diet. Allergy to all species ever tried was reported by 59%. In relation to species ever tried, cod (84%) and herring (79%) were the most frequently reported culprit species while hake (57%) and swordfish (55%) were the least frequent. A positive sIgE (value ≥ 0.35 kUA/L) to the culprit species ranged between 50% (swordfish) and 100% (hake). In tolerant patients, a negative sIgE (value < 0.35 kUA/L) ranged from 0% (hake, pollock and swordfish) to 75% (sardine). For cod, the agreement between sIgE test results and reported allergy or tolerance was 82% and 25%, respectively. Sensitization to cod parvalbumin (Gad c 1) was present in 77% of all patients.

CONCLUSION

Serological cross-reactivity between fish species is frequent, but in a significant proportion of patients, clinical relevance appears to be limited to only certain species. A well-taken history or food challenge is required for discrimination between allergy to the different fish species.

Identification of Atlantic cod (Gadus morhua), ling (Molva molva), and Alaska pollock (Gadus chalcogrammus) by PCR-ELISA using duplex PCR

Species-specific PCR-ELISA assays for the identification of Atlantic cod (Gadus morhua), Alaska pollock (Gadus chalcogrammus), and ling (Molva molva) in food products have been developed. The method, comprising a set of primers common to the first two species, a set of primers for M. molva, and a probe for each species, was designed using ND4 and cytochrome b genes as molecular markers. The sensitivity and selectivity were then determined for each assay. These assays were afterward used to analyze DNA extracted from commercial fish products. The presence of the target species was successfully detected in all analyzed samples, demonstrating the applicability of this method to the analysis of food products.

Comparative study of GH-transgenic and non-transgenic amago salmon (Oncorhynchus masou ishikawae) allergenicity and proteomic analysis of amago salmon allergens

Genetically modified (GM) foods are beneficial from the standpoint of ensuring a constant supply of foodstuffs, but they must be tested for safety before being released on the market, including by allergenicity tests to ensure that they do not contain new allergens or higher concentrations of known allergens than the same non-GM foods. In this study we used GM-amago salmon into which a growth hormone gene had been introduced and compared the allergens contained in the GM and the non-GM-amago salmons. We used a combination of Western blotting with allergen-specific antibodies and a proteomic analysis of their allergens with patients' sera, a so-called allergenome analysis, to analyze allergens. Western blotting with specific antibodies showed no increase in the content of the known allergens fish parvalbumin and fish type-I collagen in GM-amago salmon, in comparison with their content in non-GM-amago salmon. The allergenome analysis of two fish-allergic patients allowed us to identify several IgE-binding proteins in amago salmon, including parvalbumin, triose-phosphate isomerase, fructose-bisphosphate aldolase A, and serum albumin, and there were no qualitative differences in these proteins between GM and non-GM-amago salmons. These results indicate that amago salmon endogenous allergen expression does not seem to be altered by genetic modification.

New insights into seafood allergy

PURPOSE OF REVIEW

Seafood plays an important role in human nutrition worldwide, sustained by international trade of a variety of new seafood products. Increased production and consumption have resulted in more frequent reports of adverse reactions, highlighting the need for more specific diagnosis and treatment of seafood allergy. This review discusses recent literature in this field.

RECENT FINDINGS

The most recent prevalence data from Asia highlight seafood as a significant sensitizer in up to 40% of children and 33% of adults. Furthermore, the demonstration of species-specific sensitization to salt-water and fresh-water prawns and processed prawn extract should improve diagnosis. Studies on humans demonstrated for the first time that biologically active fish allergens can be detected in serum samples as early as 10 min after ingestion. These studies highlight that minute amounts of ingested seafood allergens can quickly trigger allergic symptoms; also, inhaled airborne allergens seem to induce sensitization and reactions. In the past 2 years, over 10 additional seafood allergens have been characterized. Allergen-specific detection assays in food products are available for crustacean tropomyosin; however, many specific mollusk and some fish allergens are not readily identified.

SUMMARY

Although cross-reactivity between crustacean and mollusks as well as mites is demonstrated, the often poor correlation of IgE reactivity and clinical symptoms calls for more detailed investigations. The recent development of hypoallergenic parvalbumin from carp could form the basis for safer vaccination products for treatment of fish allergy. Molecular characterization of more universal marker allergens for the three major seafood groups will improve current component-resolved clinical diagnosis and have a significant impact on the management of allergic patients, on food labeling and on future immunotherapy for seafood allergy.

Optimized techniques for the extraction of grape allergens appropriate for in vivo and in vitro testing and diagnosis

Standardized allergen extracts are needed for diagnosis and therapy purposes. For grapes, standardization is hampered by low protein and high tannin and pectin concentrations. The aim of the current study was to develop an optimized method for the extraction of grape proteins and possibly extend this to other fruits. Several existing or modified extraction methods were compared by means of protein concentration determination, SDS-PAGE, immunoblotting and radioallergosorbent test (RAST). An optimized extraction protocol was obtained in which we combined a high concentration of plant tissue, a concentrated, enriched and neutral buffer able to remove sugars and keep proteins soluble and a bivalent buffer for pectin removal. Both the quantitative (protein concentration) and qualitative parameters (SDS-PAGE protein patterns and IgE reactivity) were compared to standard protocols and commercial extracts used as diagnostic tools in the clinical practice. This method proved to be the most efficient mainly compared to the standard Björksten protocol in extracting the low molecular weight proteins, including the major grape allergen (lipid transfer protein, Vit v 1). It proved to be an easy, low cost and reproducible method proposed to prepare grape extracts that could replace the commercially available ones, used for diagnosis and possibly extend the method to other fruits especially in extracting LTPs.

Seafood allergy: lessons from clinical symptoms, immunological mechanisms and molecular biology

Food allergy consists of a wide range of disorders that result from adverse immune responses to dietary antigens. Manifestations of allergic response includes acute, potentially fatal anaphylactic reactions and a variety of chronic diseases that mainly affect the gastrointestinal tract, skin, and respiratory tract. Tools for clinical diagnosis and management, which have not changed much in the past two decades, include the clinical history, tests for specific IgE antibody to suspected foods, elimination diets, oral food challenges, and provision of medications such as epinephrine for emergency treatment. On the other hand, recent immunological and molecular biological research have enhanced our understanding of the mechanisms of these disorders and revealed the identities of many food allergens. Here, we will discuss seafood allergies with respect to the clinical manifestations, diagnosis, immunological mechanisms, and molecular biology of seafood allergens. Furthermore, potential applications and future directions in the clinical management of seafood allergies are discussed.

The effects of gastric digestion on codfish allergenicity

BACKGROUND

In a recent murine study, we showed that impaired gastric digestion supports the induction of fish allergy by protecting the digestion-sensitive major allergen parvalbumin and thus enhancing its sensitizing properties.

OBJECTIVE

The aim of the present study was to investigate whether impairment of peptic degradation might also play a role in the effector phase of codfish allergy.

METHODS

The resistance of cod proteins to digestion by simulated gastric fluid was assessed in vitro . Gastric solutions with pH values ranging from 1.25 to 5.0 were prepared, and the influence of the pH on protein degradation was evaluated by means of SDS-PAGE and IgE immunoblotting. The allergenic potency of digested and undigested cod extract was further characterized in RAST inhibition and basophil histamine release experiments.

RESULTS

The digestion experiments revealed that codfish proteins were degraded within 1 minute under physiologic gastric conditions. An only marginal pH shift from 2.5 to 2.75 abrogated completely the digestion of cod allergens. In RAST inhibition experiments digested cod extracts showed a reduced IgE-binding capability that was dependent on the digestion time. Moreover, peptic fragments expressed a 10,000 times reduced allergenic potency, as evaluated on the basis of histamine release from human basophils.

CONCLUSION

Codfish allergens have a grossly reduced ability to trigger an intestinal allergic reaction when they are physiologically degraded. Impairment of the physiologic digestion might thus lower the threshold levels of a food allergen in sensitized patients.

Characterization of allergenic food proteins for improved diagnostic methods

PURPOSE OF REVIEW

Diagnostic decision points for food allergen-specific serum IgE concentration and for skin prick test results have been established for several foods, reducing the requirement for food challenges in a number of patients. Many patients, however, still need to undergo oral food challenges because their food-specific IgE level is in the undefined range. In addition, diagnostic decision points could not be established for several foods. It appears that measurement of serum specific IgE concentrations to individual allergens is superior to determination of specific IgE to the crude food extract containing allergenic and nonallergenic proteins. This review will outline recent advantages in characterization of food allergens as well as the relevance of this knowledge for use in recently developed protein microarray technology.

RECENT FINDINGS

Protein microarrays have been developed to profile allergen-specific IgE antibodies from human serum with the advantage of screening hundreds of allergens in parallel using minute amounts of blood. This technology, however, requires prior knowledge of the proteins to be studied. The identification and characterization of clinically relevant allergens have increased dramatically within the last several years. Relevant new allergens have been identified, especially in tree nuts and seeds. Interestingly, most of these allergens belong to the same family of seed storage proteins. In addition, known food allergens have been further characterized and IgE-binding sites have been determined. Moreover, 'informative' peptides shown to be predictive for the persistence of food allergy have been identified.

SUMMARY

The combination of food allergen characterization and protein or peptide microarray technology will enable us to develop improved diagnostic tools in food allergy.

IgE-binding and cross-reactivity of a new 41 kDa allergen of codfish

BACKGROUND

A 41-kDa IgE-reactive protein (p41) was purified from raw cod extract. This protein is homologous to an aldehyde phosphate dehydrogenase (APDH). The present study aims to evaluate the IgE-binding and the cross-reactivity of this protein in 13 patients allergic to codfish.

METHODS

IgE binding of sera from 13 patients allergic to codfish was tested by Sepharose RIA and by Western blot.

RESULTS

Among the 13 patients, only 4 had specific IgE to APDH detected by APDH-Sepharose RIA. The two patients who had the highest level of specific IgE to human APDH also had a class 5-6 CAP-RAST IgE level to codfish, but two other patients with a class 5 had a negative APDH-Sepharose IgE-RIA. Relative content of APDH was higher in extracts of commercial nonfrozen fish, compared to pre rigor mortis, post rigor mortis and frozen commercial codfish. A high homology of codfish APDH was found with the corresponding human enzyme. A significant inhibition of APDH-Sepharose by human and, to a lesser extent, by rabbit APDH was observed. Western blot of APDH codfish extract showed two bands at 41 and 36 kDa, respectively.

CONCLUSIONS

We have characterized a new allergen from codfish, which had a high level of homology in different species. The p41 relative content of extracts from nonfrozen codfish was higher than in the other samples assessed.

Coupling continuous separation techniques to capillary electrophoresis

One of the weak points of capillary electrophoresis is the need to implement rigorously sample pretreatment because its great impact on the quality of the qualitative and quantitative results provided. One of the approaches to solve this problem is through the symbiosis of automatic continuous flow systems (CFSs) and capillary electrophoresis (CE). In this review a systematic approach to CFS-CE coupling is presented and discussed. The design of the corresponding interface depends on three factors, namely: (a) the characteristics of the CFS involved which can be non-chromatographic and chromatographic; (b) the type of CE equipment: laboratory-made or commercially available; and (c) the type of connection which can be in-line (on-capillary), on-line or mixed off/on-line. These are the basic criteria to qualify the hyphenation of CFS (solid-phase extraction, dialysis, gas diffusion, evaporation, direct leaching) with CE described so far and applied to determine a variety of analytes in many different types of samples. A critical discussion allows one to demonstrate that this symbiosis is an important topic in research and development, besides separation and detection, to consolidate CE as a routine analytical tool.

Meat allergy: investigation of potential allergenic proteins in beef

The potential allergenic proteins in beef were investigated. The sera of ten beef-allergic patients suffering from atopic dermatitis and having a positive RAST score to beef, aged 3-18 years, were obtained from Yoshida Hospital in Japan, and five non-allergic individuals were subjected to this study. The sera of the ten patients reacted strongly to a beef extract, but not to pork and chicken extracts by both ELISA and immunoblotting. The sera of the five control subjects did not react to any of these meat extracts. Three bands having molecular masses of approximately 200 kDa, approximately 67 kDa and approximately 60 kDa were observed by immunoblotting after SDS-PAGE. Two fractions of the beef extract from a Sephadex-gel (G-200) filtration column strongly reacted with the sera of the beef-allergic patients by ELISA and immunoblotting: one fraction had the approximately 67 kDa component and the other had the approximately 200 kDa and approximately 60 kDa components. One of them (approximately 67 kDa) was confirmed to be bovine serum albumin (BSA) by an analysis of the N-terminal amino acid sequence. We could not identify the others by sequencing, but the approximately 200 kDa and approximately 60 kDa components were presumed to be glycoproteins. Bovine gamma (BGG:globulin M.W. approximately 160 kDa) is a glycoprotein and has several subunits. The beef-allergic patients showed strong reactivity to the approximately 200 kDa and approximately 60 kDa components of pure BGG by immunoblotting. Inhibition-ELISA showed that pure BGG preparations strongly inhibited the binding of sera from the beef-allergic patients to the beef extract. These results suggest that the approximately 200 kDa, approximately 67 kDa and approximately 60 kDa components in the beef extract had strong allergenicity: approximately 67 kDa was BSA, and approximately 200 kDa and approximately 60 kDa were presumably aggregated BGG and it's heavy chain, respectively.

One-step purification of R-phycoerythrin from the red macroalga Palmaria palmata using preparative polyacrylamide gel electrophoresis

Phycoerythrin is a major light-harvesting pigment of red algae and cyanobacteria widely used as a fluorescent probe. In this study, phycoerythrin of the red macroalga Palmaria palmata was extracted by grinding the algal sample in liquid nitrogen, homogenisation in phosphate buffer and centrifugation. Phycoerythrin was then purified from this crude extract using preparative polyacrylamide gel electrophoresis (PAGE) with a continuous elution system and detected by its pink colour and fluorescence. The pigment presented a typical spectrum of R-phycoerythrin, with three absorbance maxima at 499, 545 and 565 nm, and displayed a fluorescence maximum at 578 nm. The absorbance ratio A565/A280, a criterion for purity, was 3.2. A single protein of relative molecular mass 240,000 was detected on native-PAGE with silver staining. Sodium dodecyl sulphate-PAGE demonstrated the presence of two major subunits with Mr 20,000 and 21,000, respectively, and a very minor subunit of Mr 30,000. These observations are consistent with the (alphabeta)6gamma subunit composition characteristic of R-phycoerythrin. Phycoerythrin of Palmaria palmata was determined to be present in larger amounts in autumn and showed a good stability up to 60 degrees C and between pH 3.5 and 9.5. In conclusion, phycoerythrin of Palmaria palmata was purified in a single-step using preparative PAGE. Obtaining pure R-phycoerythrin of Palmaria palmata will allow one to evaluate its fluorescence properties for future applications in biochemical techniques.